usb_cdc: Add usb_read_ep0_setup() interface function

Use new usb_read_ep0_setup() function when reading a setup packet -
this allows the low-level usb hardware code to better handle errors.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/generic/usb_cdc.c

@@ -412,9 +412,8 @@ static void
 usb_state_ready(void)
 {
     struct usb_ctrlrequest req;
-    int_fast8_t ret = usb_read_ep0(&req, sizeof(req));
+    int_fast8_t ret = usb_read_ep0_setup(&req, sizeof(req));
     if (ret != sizeof(req))
-        // XXX - should verify that packet was sent with a setup token
         return;
     switch (req.bRequest) {
     case USB_REQ_GET_DESCRIPTOR: usb_req_get_descriptor(&req); break;

src/generic/usb_cdc.h

@@ -15,6 +15,7 @@ enum {
 int_fast8_t usb_read_bulk_out(void *data, uint_fast8_t max_len);
 int_fast8_t usb_send_bulk_in(void *data, uint_fast8_t len);
 int_fast8_t usb_read_ep0(void *data, uint_fast8_t max_len);
+int_fast8_t usb_read_ep0_setup(void *data, uint_fast8_t max_len);
 int_fast8_t usb_send_ep0(const void *data, uint_fast8_t len);
 int_fast8_t usb_send_ep0_progmem(const void *data, uint_fast8_t len);
 void usb_stall_ep0(void);

src/lpc176x/usbserial.c

@@ -189,6 +189,12 @@ usb_read_ep0(void *data, uint_fast8_t max_len)
     return usb_read_packet(EP0OUT, data, max_len);
 }
 
+int_fast8_t
+usb_read_ep0_setup(void *data, uint_fast8_t max_len)
+{
+    return usb_read_ep0(data, max_len);
+}
+
 int_fast8_t
 usb_send_ep0(const void *data, uint_fast8_t len)
 {

src/samd21/usbserial.c

@@ -127,6 +127,12 @@ usb_read_ep0(void *data, uint_fast8_t max_len)
     return usb_read_packet(0, 0, data, max_len);
 }
 
+int_fast8_t
+usb_read_ep0_setup(void *data, uint_fast8_t max_len)
+{
+    return usb_read_ep0(data, max_len);
+}
+
 int_fast8_t
 usb_send_ep0(const void *data, uint_fast8_t len)
 {